There is a need to clean lubricated vapor compression systems and their components during manufacture and service.
Vapor compression systems are well known in the art. They are used in a wide variety of applications such as heating, air conditioning, and refrigeration. By compressing and expanding a heat transfer agent or refrigerant, these systems absorb and release heat according to the needs of a particular application. Common components of a vapor compression system include: vapor or gas compressors; liquid pumps; heat-transfer equipment such as gas coolers, intercoolers, aftercoolers, exchangers, economizers; vapor condensers, such as reciprocating piston compressors, rotating screw compressors, centrifugal compressors, and scroll compressors; evaporators; liquid coolers and receivers; expanders; control valves and pressure-drop throttling devices such as capillaries; refrigerant-mixture separating chambers; steam-mixing chambers; and connecting piping and insulation. These components are typically fabricated from copper, brass, steel and conventional gasket materials.
Since vapor compression systems have sliding, rotating or other moving components, most require the use of a lubricant which is mixed with the refrigerant. There is a need from time to time to clean such systems and their components by removing the lubricants from their surfaces. Such a need arises, for example, during the retrofit of a chlorofluorocarbon (CFC) or hydrochlorofluorocarbon (HCFC) refrigerant to a hydrofluorocarbon (HFC) refrigerant, and during service, especially after a catastrophic event such as compressor burnout. There is also a need to clean such systems during manufacture.
Until recently, chlorofluorocarbons (CFCs), such as trichloromethane (R-11), were used as cleaning agents for such systems. Although effective, CFCs are now considered environmentally unacceptable because they contribute to the depletion of the stratospheric ozone layer. As the use of CFCs is reduced and ultimately phased out, new cleaning agents are needed that not only perform well, but also pose no danger to the ozone layer.
A number of environmentally acceptable solvents have been proposed, but their use has been met with limited success. For example, organic solvents, such as hexane, have good cleaning properties and do not deplete the ozone layer, but they are flammable. Aqueous-based cleaning compositions have zero ozone depletion potential and are non-flammable, but they tend to be difficult to remove from the cleaned surfaces due to their relatively low volatility and the presence therein of additives that leave a residue. Additionally, aqueous-based cleaning compositions are often inadequate for cleaning typical organic soils that are present in vapor compression systems. Terpene-based solvents, like aqueous-based cleaning compositions, are difficult to remove from the system.
Therefore, a need exists for the identification of environmentally-acceptable cleaning agents that effectively clean vapor compression systems. The present invention fulfills this need.